Role of Electrotonic Coupling in the Olivocerebellar System

De rol van electrotone koppeling in het olivocerebellaire systeem

The level of electrotonic coupling in the inferior
olive is higher than in any other brain region. Connexin36 is the
main protein that forms the olivary gap junctions. Yet, the functional
role of electrotonic coupling in the cerebellar motor control remains
to be determined. In this thesis mice that lack coupling among their
olivary neurons were subjected to classical eyeblink conditioning.
Cx36 deficient mice showed impaired learning-dependent timing in that
they were not able to fix the timing of their conditioned responses at
the moment when the unconditioned stimulus is about to occur. The
timing of spike activities generated in the olive of coupling-
deficient mice was abnormal in that their latencies in response to the
unconditioned stimulus were inconsistent and that their overall
synchrony was reduced. Whole cell recordings of olivary neurons in
vivo showed that these different spiking activities over time result
in part from altered interaction!
s with their subthreshold oscillations. These results, combined with
analysis of olivary activities in a computer simulation of the
cerebellar system, suggest that electrotonic coupling among olivary
neurons is necessary for proper synchronous oscillations in the
inferior olive, which in turn determine the pace of the olivary
responses necessary for learning-dependent timing in cerebellar motor
control.